In oil and gas exploration and mining industries it is sometimes useful to process solids or cuttings that are excavated or drilled from geological deposits below a body of water. In subsea drilling, for, example, it is possible to remove drilled cuttings from the ocean floor using subsea pumps that return to the surface geological solids entrained in drilling mud.
One difficulty associated with such processes is the tendency of solids undesirably to plug or block processing apparatus, including pumps and flow conduits. In some cases, blockage is due to the excessive size of the solids particles. In other instances the nature of the solids may cause them to adhere to processing equipment, flow conduits or cutting blades, which may result in blockage or shutdown of operations. When a blockage occurs it is costly and time consuming to clear the blockage.
United States patent published application US 2010/0147593 A1 is directed to a subsea solids processing unit having a housing with cutters for reducing the size of solids entrained in a drilling mud.
A publication entitled “SubSea MudLift Drilling Joint Industry Project: Delivering Dual Gradient Drilling Technology to Industry”, Society of Petroleum Engineers, SPE 71357 (2001: Annual Technical Conference and Exhibition, New Orleans, La.) describes the use of a horizontally offset mudlift pump and solids handling mechanism. FIG. 5 illustrates the use of a horizontally offset mudlift pump that is offset some distance from the drill pipe and riser assembly. Solids entrained in drilling mud first are transported by a flow conduit away from the drill pipe and riser for processing. Then, the solids are pumped by way of a return line to the water surface.
Another publication, “SubSea MudLift Drilling: Design and Implementation of a Dual Gradient Drilling System”, Society of Petroleum Engineers, SPE 71359, (2001: Annual Technical Conference and Exhibition, New Orleans, La.) describes the use of a solids processing unit (SPU) integrated into a Subsea Mudlift Drilling (SMD) system deployed in connection with a very large 185,000 pound mudlift pump (MLP) package.
A significant challenge in the drilling of wells over water is to reduce time and effort in deploying equipment into the water to prepare for and conduct drilling operations. It is desirable to deploy equipment that may be easily and conveniently placed in the water from an mobile offshore, drilling unit, or MODU. Furthermore, in the processing and transportation of drilled cuttings for operations conducted in water it is desirable to reduce the likelihood of forming undesirable blockages within mud/solids flow conduits and a solids processing unit. In general, the total length of a conduit and the number of angles or turns in a flow conduit increases the likelihood of a blockage within a conduit. Further, it is known that various types of debris may be transported a solids, processing unit, and it is desirable to reduce the likelihood of blockage within a solids processing device. Certain types of soil are known to have a tendency to adhere to processing equipment, which in some instances could cause a flow blockage. It would be desirable to devise a reliable and effective method for cleaning the inside of a subsea solids processing apparatus without removing the unit from the water, and pulling the unit out of service.